Thionine

Thionine, also known as thionine acetate or Lauth's violet, is a strongly staining metachromatic dye, featuring a phenothiazine core, that is widely used for biological staining. Thionine can also be used in place of Schiff reagent in quantitative Feulgen staining of DNA. It can also be used to mediate electron transfer in microbial fuel cells. The dye's name is frequently misspelled, with omission of the e. The -ine ending indicates that the compound is an amine.